Stretch nonwoven fabric and method for production thereof

ABSTRACT

A spunbonded elastic nonwoven fabric according to the invention comprises fibers formed from a polymer comprising a thermoplastic polyurethane elastomer, wherein the thermoplastic polyurethane elastomer has a solidifying point of 65° C. or above as measured by a differential scanning calorimeter (DSC) and contains 3.00×10 6  or less polar-solvent-insoluble particles per g as counted on a particle size distribution analyzer, which is based on an electrical sensing zone method, equipped with an aperture tube having an orifice of 100 μm in diameter, and wherein the fibers have diameters such that the standard deviation of fiber diameters (Sn) divided by the average fiber diameter (X ave ) (Sn/X ave ) gives a value of 0.15 or less.

FIELD OF THE INVENTION

The present invention relates to an elastic nonwoven fabric obtainableby spunbonding a polymer that contains a thermoplastic polyurethaneelastomer, a production method for the same, and a hygiene materialincluding the elastic nonwoven fabric.

BACKGROUND OF THE INVENTION

Elastic nonwoven fabrics made from thermoplastic polyurethane elastomers(hereinafter “TPU”) proposed so far have been used in applicationsincluding garments, hygiene materials and materials for sporting goodsdue to their high elasticity, low residual strain and superiorbreathability.

Meltblowing is a typical process for producing elastic nonwoven fabricsfrom TPU. Meltblown elastic nonwoven fabrics exhibit high elasticity,flexibility and breathability, and therefore they have been used inrelatively active applications that require conformity to bodymovements, such as side bands in disposable diapers, gauze pads inadhesive bandages, and disposable gloves.

JP-A-7-503502 discloses a spunbonded nonwoven fabric comprising a web ofelastomeric thermoplastic substantially continuous filaments. Thisspunbonded nonwoven fabric is mentioned to have a more pleasant feelthan meltblown nonwoven fabrics because they more closely approximatetextile fiber diameters and consequently textile-like drape and hand.JP-A-7-503502 describes thermoplastic polyurethane elastomers as thethermoplastic elastomers, but it is not disclosed solidifying points ofthese elastomers and particle number of polar-solvent insolubles. Aswill be illustrated in Comparative Examples 1 and 2 of thisspecification, fibers will break and adhere to one another duringspinning when the thermoplastic elastomer has a solidifying point ofless than 60° C., or contains over 3.00×10⁶ particles of polar-solventinsolubles per g of the elastomer; the result is a nonwoven fabrichaving bad touch.

JP-A-9-87358 discloses a thermoplastic polyurethane resin that contains,per g of the resin, 2×10⁴ or less particles of polar-solvent insolublesranging from 6 to 80 μm in particle diameters. This thermoplasticpolyurethane resin has been shown to be useful for producing elasticpolyurethane fibers without causing any increase in nozzle back pressureand any filament breakage during the melt spinning. The presentinventors have tried to produced the thermoplastic polyurethane resinaccording to JP-A-9-87358, but they cannot obtain it.

JP-A-2002-522653 addresses the characteristic “sticky” nature of thethermoplastic elastomers as one of the problems encountered inspunbonding the elastomers into nonwoven fabrics. It has been pointedout that turbulence in the air can bring filaments into contact and theycan adhere to one another in the spunbonding. The “stickiness” has beenproven to be especially troublesome during rolling up of the webs.Further, JP-A-2002-522653 mentions breakage and elastic failure of thestrand during extrusion and/or stretching. As will be illustrated inComparative Example 2 of this specification, spinning TPU (Elastollan1180A (BASE Japan Ltd.)) described in JP-A-2002-522653 is accompaniedwith filament breakage and the resultant nonwoven fabric isunsatisfactory.

WO99/39037 discloses an elastic nonwoven fabric comprised of athermoplastic polyurethane resin that has a hardness (JIS-A hardness) of65 A to 98 A and a fluidization initiation temperature of 80 to 150° C.This nonwoven fabric is obtained by stacking continuous filaments of athermoplastic polyurethane resin into a sheet form and fusion-bondingthe stacked filaments at the contact points by their own heat. Thisproduction is the meltblowing. The present inventors performed theprocedure described in WO99/39037 to prepare a thermoplasticpolyurethane resin and used it in Comparative Example 4 to form aspunbonded nonwoven fabric. The result was filament breakage during thespinning and the resultant nonwoven fabric was of inferior quality.

JP-A-9-291454 discloses elastic nonwoven fabrics, having excellentdrape, comprising a conjugate fiber comprising a crystallinepolypropylene and a thermoplastic elastomer. It discloses an elasticnonwoven fabric which comprises a concentric sheath-core conjugate fibermade up of 50 wt % of a urethane elastomer as the core and 50 wt % of apolypropylene as the sheath (Example 6). The disclosure extends to anelastic nonwoven fabric which comprises a conjugate fiber made up of 50wt % of a urethane elastomer and 50 wt % of a polypropylene to show asix-segmented cross section (Example 8). These nonwoven fabrics areproduced by opening staple fibers with a carder and heating them with athrough-air dryer. They are capable of about 75% elastic recovery after20% elongation and have excellent drape. However, they are stillinsufficient in elastic properties for applications such as garments,hygiene materials and materials for sporting goods.

OBJECT OF THE INVENTION

The present invention is aimed at solving the aforesaid problemsassociated with the background art. Thus, it is an object of theinvention to provide an elastic nonwoven fabric that is obtained byspunbonding a polymer containing a thermoplastic polyurethane elastomerand has pleasant touch, high elasticity and small residual strain. It isanother object of the invention to provide a production method for theelastic nonwoven fabric.

DISCLOSURE OF THE INVENTION

The present inventors earnestly studied to overcome the aforesaidproblems, and completed the present invention based on the finding thatthe use of a thermoplastic polyurethane elastomer having a specificsolidifying point and a specific content of polar-solvent insolubles canlead to a nonwoven fabric that has narrow fiber diameter distributionand as a consequence has pleasant touch.

An elastic nonwoven fabric according to the invention is a spunbondedelastic nonwoven fabric comprising fibers formed from a polymercomprising a thermoplastic polyurethane elastomer, said thermoplasticpolyurethane elastomer having a solidifying point of 65° C. or above asmeasured by a differential scanning calorimeter (DSC) and containing3.00×10⁶ or less polar-solvent-insoluble particles per g as counted on aparticle size distribution analyzer, which is based on an electricalsensing zone method, equipped with an aperture tube having an orifice of100 μm in diameter, and said fibers having diameters such that thestandard deviation of fiber diameters (Sn) divided by the average fiberdiameter (X_(ave)) (Sn/X_(ave)) gives a value of 0.15 or less.

The polymer preferably contains the thermoplastic polyurethane elastomerin an amount of 10 wt % or more.

On the thermoplastic polyurethane elastomer, a total heat of fusion (a)determined from endothermic peaks within the temperature range of from90 to 140° C. and a total heat of fusion (b) determined from endothermicpeaks within the temperature range of from above 140 to 220° C., whichare measured by a differential scanning calorimeter (DSC), preferablysatisfy the following relation (1):a/(a+b)×100≦80   (1).

A hygiene material according to the invention includes the elasticnonwoven fabric.

A production method for elastic nonwoven fabrics according to theinvention comprises fibers formed from a polymer comprising athermoplastic polyurethane elastomer by spunbonding the polymer whereinthe thermoplastic polyurethane elastomer has a solidifying point of 65°C. or above as measured by a differential scanning calorimeter (DSC) andcontains 3.00×10⁶ or less polar-solvent-insoluble particles per g ascounted on a particle size distribution analyzer, which is based on anelectrical sensing zone method, equipped with an aperture tube having anorifice of 100 μm in diameter, and wherein the fibers have diameterssuch that the standard deviation of fiber diameters (Sn) divided by theaverage fiber diameter (X_(ave)) (Sn/X_(ave)) gives a value of 0.15 orless.

A spunbonding processible thermoplastic polyurethane elastomer accordingto the invention has a solidifying point of 65° C. or above as measuredby a differential scanning calorimeter (DSC), contains 3.00×10⁶ or lesspolar-solvent-insoluble particles per g as counted on a particle sizedistribution analyzer, which is based on an electrical sensing zonemethod, equipped with an aperture tube having an orifice of 100 μm indiameter, and enables production of spunbonded elastic nonwoven fabricsin which the standard deviation of fiber diameters (Sn) divided by theaverage fiber diameter (X_(ave)) (Sn/X_(ave)) gives a value of 0.15 orless.

EFFECT OF THE INVENTION

Spunbonding a polymer can be performed stably with no filament breakageand no fibers adhering one another or adhering to the spinning towerwall, by incorporating the polymer with a thermoplastic polyurethaneelastomer that has a specific solidifying point and a specific contentof polar-solvent insolubles. Also, the use of the thermoplasticpolyurethane elastomer leads to fiber diameters with narrow distributionso that the resultant spunbonded nonwoven fabric can display excellenttouch.

PREFERRED EMBODIMENTS OF THE INVENTION Elastic Nonwoven Fabric

The elastic nonwoven fabric of the invention is obtained by spunbondinga polymer that contains a thermoplastic polyurethane elastomer with aspecific solidifying point and a specific content of polar-solventinsolubles. The nonwoven fabric has a fiber diameter distribution withina certain range.

<Thermoplastic Polyurethane Elastomer>

The thermoplastic polyurethane elastomer (TPU) has a solidifying pointof 65° C. or above, preferably 75° C. or above, and optimally 85° C. orabove. The upper limit on the solidifying point is preferably 195° C.The solidifying point as used herein is measured by a differentialscanning calorimeter (DSC), and is a temperature at which an exothermicpeak attributed to solidification of the TPU appears while the TPU isbeing cooled at a rate of 10° C./min after heated to 230° C. at a rateof 10° C./min and at 230° C. for 5 minutes. The TPU having a solidifyingpoint of 65° C. or above can prevent defects such as fusion bondedfibers, broken filaments and resin masses in the spunbonding, and canprevent nonwoven fabrics to adhere to a embossing roll in a thermalembossing. In addition, the resultant nonwoven fabrics are less sticky,so that they are suitably used in materials which bring into contactwith a skin, such as garments, hygiene materials and materials forsporting goods. On the other hand, when the TPU has a solidifying pointof 195° C. or below, the processing properties are improved. Asolidifying point of a fiber tends to be higher than that of the TPUused.

In order that the TPU can have a solidifying point of not less than 65°C., optimum chemical structures are to be selected for its materials: apolyol, an isocyanate compound and a chain extender. In addition, theamount of hard segments should be carefully controlled. The amount ofhard segments (wt %) is determined by dividing the total weight of theisocyanate compound and the chain extender with the total weight of thepolyol, the isocyanate compound and the chain extender, andcentuplicating the quotient. The amount of hard segments is preferably20 to 60 wt %, more preferably 22 to 50 wt %, and optimally 25 to 48 wt%.

In the TPU, particles that are insoluble in a polar solvent totals3.00×10⁶ or less per g of TPU, preferably 2.50×10⁶ or less per g of TPU,and optimally 2.00×10⁶ or less per g of TPU. The polar-solventinsolubles are mainly aggregates such as fish-eyes and gels that aregenerated in a TPU production. The aggregates are components derivedfrom the materials for the TPU and reaction products among thosematerials. Examples of such polar-solvent insolubles include derivativesfrom agglomerated hard segments, and hard segments and/or soft segmentscrosslinked together through allophanate linkages or biuret linkages.

The polar-solvent-insoluble particles are the insolubles occurring whenthe TPU is dissolved in dimethylacetamide (hereinafter “DMAC”) as asolvent. They are counted on a particle size distribution analyzer,which utilizes an electrical sensing zone method, with an aperture tube100 μm in diameter. The aperture tube having a 100 μm pore can allowdetection of particles which are 2 to 60 μm in terms of uncrosslinkedpolystyrene, and those particles are counted. The present inventors havefound that the particle sizes in this range are closely related to thespinning stability for TPU-containing fiber and the quality of theresulting elastic nonwoven fabric. When the polar-solvent-insolubleparticles are 3.00×10⁶ or less per g of TPU, the TPU having theaforesaid solidifying point can prevent problems such as widedistribution of fiber diameter and filament breakage during thespinning. When such TPU has been spun, the fiber will have diameterequivalent to that of ordinary fabrics so that the resultant nonwovenfabric will have a superior touch, being suitable for hygiene materialsand like items. Moreover, the TPU containing the polar-solvent-insolubleparticles in the suitable number is difficult to clog a filter forimpurities fitted in an extruder. This requires less frequent adjustmentand maintenance of the apparatus, and is industrially preferred.

The TPU containing lesser polar-solvent-insolubles can be prepared byfiltration of a crude TPU given after polymerization of a polyol, anisocyanate compound and a chain extender.

With respect to the TPU, a total heat of fusion (a) determined fromendothermic peaks within the temperature range of from 90 to 140° C. anda total heat of fusion (b) determined from endothermic peaks within thetemperature range of from above 140 to220° C., which are measured on adifferential scanning calorimeter (DSC), preferably satisfy the relation(1):a/(a+b)×100≦80   (1);more preferably satisfy the relation (2):a/(a+b)×100≦70   (2);and optimally satisfy the relation (3):a/(a+b)×100≦55   (3)wherein the left hand side “a/(a+b)×100” represents a ratio (%) of theheat of fusion attributed to the hard domains in the TPU.

When the above relational formula gives 80 or less, fibers, particularlyspunbonded fibers, and nonwoven fabrics have improved strength andhigher elasticity. In the invention, the lower limit on this ratio ofthe heat of fusion attributed to the hard domains in the TPU is suitablyaround 0.1.

The TPU preferably ranges in melt viscosity from 100 to 3000 Pa·s, morepreferably from 200 to 2000 Pa·s, and optimally from 1000 to 1500 Pa·sas measured at 200° C. and 100 sec⁻¹ shear rate. The melt viscosity is avalue determined by the use of a Capirograph (Toyo Seiki K. K., nozzlelength: 30 mm, nozzle diameter: 1 mm).

The TPU preferably has a water content of 350 ppm or less, morepreferably 300 ppm or less, and optimally 150 ppm or less. The TPUhaving a water content of 350 ppm or less can inhibits bubbles frombeing mixed into the strands and the filaments from breaking in theproduction of nonwoven fabrics with a large spunbonding machine.

<Production Method for Thermoplastic Polyurethane Elastomer>

As described hereinabove, the thermoplastic polyurethane elastomer maybe produced from a polyol, an isocyanate compound and a chain extenderthat have optimal chemical structures. Exemplary processes for theproduction of the TPU include:

(i) a “prepolymer process” in which a polyol and an isocyanate compoundare preliminarily reacted to give an isocyanato-terminated prepolymer(hereinafter “prepolymer”) and the prepolymer is reacted with a chainextender; and

(ii) a “one-shot process” in which a polyol and a chain extender arepreviously mixed and the mixture is reacted with an isocyanate compound.

Of these two, the prepolymer process is more preferable in view ofmechanical characteristics and quality of the resultant TPU.

In the prepolymer process, the polyol and the isocyanate compound aremixed by stirring in the presence of an inert gas at around 40 to 250°C. for approximately 30 seconds to 8 hours to give a prepolymer; thenthe prepolymer is sufficiently mixed by high speed agitation with thechain extender in proportions such that the isocyanate index will bepreferably 0.9 to 1.2, more preferably 0.95 to 1.15, and stillpreferably 0.97 to 1.08. Polymerization may be made at appropriatetemperatures depending on the melting point of the chain extender andthe viscosity of the prepolymer. For example, the polymerizationtemperature will be in the range of around 80 to 300° C., preferably 80to 260° C., and optimally 90 to 220° C. The polymerization time willpreferably range from about 2 seconds to 1 hour.

In the one-shot process, the polyol and the chain extender are mixedtogether and then degassed; thereafter the mixture is polymerized withthe isocyanate compound by being stirred together at 40 to 280° C.,preferably 100 to 260° C., for approximately 30 seconds to 1 hour. Theisocyanate index in the one-shot process is preferably in the same rangeas in the prepolymer process.

<TPU Production Equipment>

The TPU may be continuously produced by reaction extrusion in aequipment comprised of a material storage tanks section, a mixersection, a static mixers section and a pelletizer section.

The material storage tanks section includes an isocyanate compoundstorage tank, a polyol storage tank, and a chain extender storage tank.Each storage tank is connected to a high-speed stirrer or a staticmixers section (mentioned later) through a supply line having a gearpump and a downstream flow meter.

The mixer section has a mixing means such as a high-speed stirrer. Thehigh-speed stirrer is not particularly limited if it is capable ofhigh-speed mixing the aforesaid materials. Preferably, when thehigh-speed stirrer tank is equipped with a blade 4 cm in diameter and 12cm around, it is capable of 300 to 5000 rpm (circumferential speed: 100to 600 m/min), and desirably 1000 to 3500 rpm (circumferential speed:120 to 420 m/min). The high-speed stirrer is preferably equipped with aheater (or a jacket) and a temperature sensor in order to detect changesin temperature in the stirring tank by means of the temperature sensorand accordingly condition the temperature by the heater.

The mixer section may optionally include a reaction pot, where themixture of materials resulting from the high-speed stirring istemporarily kept to promote prepolymerization. The reaction potpreferably has a temperature control means. The reaction pot ispreferably provided between the high-speed stirrer and a first staticmixer in the most upstream position in the static mixers section.

The static mixers section preferably consists of plural static mixersconnected in series. The static mixers (designated as the first staticmixer 1, the second static mixer 2, the third static mixer 3, etc. fromthe upstream in the traveling direction for the materials) may havemixing elements of various figurations without limitation. For example,“Kagaku Kogaku no Shimpo (Advance of Chemical Engineering)” Vol. 24,Stirring and Mixing (edited by The Society of Chemical Engineers, Japan,Tokai Branch, and published from Maki Shoten on Oct. 20, 1990, firstedition), in FIG. 10.1.1 on Page 155, illustrates Company-N type,Company-T type, Company-S type and Company-T type figurations. Thestatic mixer having right element and left element arranged alternatelyis preferable. Optionally, the neighboring static mixers are connectedby a straight pipe.

Each static mixer will range in length from 0.13 to 3.6 m, preferably0.3 to 2.0 m, and more preferably 0.5 to 1.0 m, and have an innerdiameter of 10 to 300 mm, preferably 13 to 150 mm, and more preferably15 to 50 mm. The ratio of length to inner diameter (L/D) will range from3 to 25, and preferably from 5 to 15. Each static mixer is preferablymade of a substantially non-metallic material, such as fiber-reinforcedplastic (FRP), in at least the liquid contact part thereof. Alsopreferably, each static mixer is coated with a fluorine-based resin,such as polytetrafluoroethylene, in at least the liquid contact partthereof. When the static mixers have the substantially non-metallicliquid contact parts, the polar-solvent insolubles are effectivelyprevented from occurring in the TPU. Exemplary static mixers includemetallic static mixers whose inner walls are protected withfluorine-based resin tubes such as polytetrafluoroethylene tubes, and MXseries commercially available from Noritake Company, Ltd.

Each static mixer is preferably equipped with a heater (or a jacket) anda temperature sensor in order to detect changes in temperature in themixer by means of the temperature sensor and accordingly condition thetemperature by the heater. This structure enables temperature controlfor individual static mixers depending on the composition of thematerials. Accordingly, in the reduced catalyst amount, the TPU can beproduced under optimum reaction conditions.

The first static mixer 1 in the most upstream position in the staticmixers section is connected to the high-speed stirrer or the reactionpot of the mixer section. And the most downstream static mixer in thestatic mixers section is connected to a strand die of the pelletizersection or a single-screw extruder. The static mixers may be connectedtogether in an arbitrary number depending on a desired mixing effect tomeet the objective use of the TPU and the composition of the materials.For example, the static mixers may be serially connected 3 to 25 m long,and preferably 5 to 20 m long, or in 10 to 50 units, and preferably 15to 35 units. Gear pumps may be optionally provided between the staticmixers to control the flow rate.

The pelletizer section may be constituted with a known pelletizer suchas an underwater pelletizer, or with a strand die and a cutter.

A single-screw extruder may be optionally arranged between the staticmixers section and the pelletizer section in order to further knead thereaction product discharged from the static mixers section.

<TPU Production Method>

The TPU may be produced using an equipment as described above. Forexample, a mixture containing at least the isocyanate compound and thepolyol is forced through the static mixers together with the chainextender, and these materials are polymerized as they mix together.Particularly preferably, polymerization will be made by a series ofsteps in which the isocyanate compound and the polyol are sufficientlymixed together in a high-speed stirrer and then further mixed with thechain extender by a high-speed stirrer, and these materials are reactedwith each other while traveling through the static mixtures. Alsopreferably, the isocyanate compound and the polyol are first reacted toprepare a prepolymer, then the prepolymer is mixed with the chainextender in a high-speed stirrer, and the mixture is reacted in thestatic mixers.

The isocyanate compound and the polyol will be mixed together in ahigh-speed stirring tank at a residence time of 0.05 to 0.5 minute,preferably 0.1 to 0.4 minute, and at 60 to 150° C., preferably 80 to140° C. When the mixture of the isocyanate compound and the polyol iskept in the reaction pot to promote prepolymerization, the residencetime will be 0.1 to 60 minutes, and preferably 1 to 30 minutes, and thetemperature will range from 80 to 150° C., and preferably from 90 to140° C.

In either case, the mixture of the isocyanate compound and the polyol isfed together with the chain extender into the static mixtures to bepolymerized. They may be fed to the static mixtures individually orafter mixed together in a high-speed stirrer. As described earlier, theisocyanate compound and the polyol may be preliminarily reacted to givea prepolymer, and the prepolymer and the chain extender may beintroduced into the static mixers with polymerization. The static mixerswill have inside temperatures of 100 to 300° C., and preferably 150 to280° C. The feed rate for the materials or the reaction product will bedesirably set at 10 to 200 kg/h, and preferably 30 to 150 kg/h.

There are other processes useful to produce the TPU according to theinvention. For example, the isocyanate compound, the polyol and thechain extender may be sufficiently mixed in a high-speed stirrer, andthe mixture is continuously discharged on a belt and thereafter heatedto induce polymerization.

These production processes afford the TPU containing lesser amount ofthe polar-solvent insolubles such as fish eye. The polar-solventinsolubles may be reduced by filtering the TPU. For example, thesufficiently dried TPU in pellet form may be extruded through an outlethead fitted with a filtering medium such as a metal mesh, a metallicnonwoven fabric or a polymer filter, thus filtering out the insolubles.The filtration can reduce the polar-solvent-insoluble particles to about3×10⁴ particles per g of TPU (lower limit). The extruder is preferably asingle-screw extruder or a multi-screw extruder. The metal mesh usuallyhas 100 meshes or above, preferably 500 meshes or above, and morepreferably 1000 meshes or above. A plural metal meshes which have thesame or different mesh size each other are preferably used in piles. Thepolymer filters include Fuji Duplex Polymer Filter System (FUJI FILTERMGF. CO., LTD.), ASKA Polymer Filter System (ASKA Corporation) and DENAFILTER (NAGASE & CO. LTD.).

The TPU resulting from the above method may be crushed or finely dividedby means of a cutter or a pelletizer, and then may be fabricated intodesired shapes with an extruder or an injection molding machine.

<Polyol>

The polyol used in the production of the TPU is a polymer having two ormore hydroxyl groups in the molecule. Examples thereof includepolyoxyalkylene polyols, polytetramethylene ether glycols, polyesterpolyols, polycaprolactone polyols and polycarbonate diols. These may beused singly or in combination of two or more kinds. Polyoxyalkylenepolyols, polytetramethylene ether glycols and polyester polyols arepreferable.

The polyols are preferably dehydrated by being heated under reducedpressure until the water content lowers to a sufficient level. The watercontent will be preferably reduced to 0.05 wt % or below, morepreferably 0.03 wt % or below, and even more preferably 0.02 wt % orbelow.

(Polyoxyalkylene Polyols)

Exemplary polyoxyalkylene polyols include polyoxyalkylene glycols, whichare addition polymerized one or more relatively low-molecular weightdivalent alcohols with alkylene oxides such as propylene oxide, ethyleneoxide, butylene oxide and styrene oxide. Preferred polymerizationcatalysts include an alkali metal compound, such as cesium hydroxide orrubidium hydroxide, or a P═N having compound.

Of the aforesaid alkylene oxides, propylene oxide and ethylene oxide areparticularly preferred. When two or more alkylene oxides are used, thepropylene oxide will preferably account for at least 40 wt %, and morepreferably at least 50 wt % of the total amount of alkylene oxides. Whenthe alkylene oxides contain the propylene oxide in the above amount, thepolyoxyalkylene polyol can contain oxypropylene groups in an amount of40 wt % or more.

In order to attain higher durability and mechanical properties of theTPU, the polyoxyalkylene polyol will be preferably treated to convert atleast 50 mol %, and more preferably at least 60 mol % of its molecularterminals to primary hydroxyl groups. Copolymerization withethyleneoxide at molecular terminals is a suitable way to achieve adesired level of conversion to the primary hydroxyl groups.

The polyoxyalkylene polyol used in the TPU production preferably rangesin number-average molecular weight from 200 to 8000, and more preferablyfrom 500 to 5000. From the viewpoints of lowering the glass transitiontemperature and improving the fluidity of the TPU, two or morepolyoxyalkylene polyols with different molecular weights and oxyalkylenegroup contents will be preferably used as a mixture in the production ofthe TPU. Moreover, the polyoxyalkylene polyol preferably contains alesser amount of terminally unsaturated monols, the byproducts fromaddition polymerization with propylene oxide. The monol content in thepolyoxyalkylene polyol is expressed as a degree of unsaturation asdescribed in JIS K-1557. The polyoxyalkylene polyol preferably has anunsaturation degree of 0.03 meq/g or below, and more preferably 0.02meq/g or below. When the unsaturation degree exceeds 0.03 meq/g, the TPUtends to have poorer heat resistance and durability. The lower limit onthe unsaturation degree will be suitably around 0.001 meq/g inconsideration of the industrial production of polyoxyalkylene polyol.

(Polytetramethylene Ether Glycols)

The polyol may be polytetramethylene ether glycol (hereinafter “PTMEG”)resulting from ring opening polymerization of tetrahydrofuran. PTMEGpreferably has a number-average molecular weight of about 250 to 4000,and particularly preferably about 250 to 3000.

(Polyester Polyols)

Exemplary polyester polyols include polymers resulted from condensationbetween one or more low-molecular weight polyols and one or morecarboxylic acids selected from low-molecular weight dicarboxylic acidsand oligomer acids.

The low-molecular weight polyols include ethylene glycol, diethyleneglycol, propylene glycol, dipropylene glycol, 1,3-propanediol,1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, glycerol,trimethylolpropane, 3-methyl-1,5-pentanediol, hydrogenated bisphenol Aand hydrogenated bisphenol F. The low-molecular weight dicarboxylicacids include glutaric acid, adipic acid, sebacic acid, terephthalicacid, isophthalic acid and dimer acid. Specific examples of thepolyester polyols include polyethylene butylene adipate polyol,polyethylene adipate polyol, polyethylene propylene adipate polyol andpolypropylene adipate polyol.

The polyester polyols preferably range in number-average molecularweight approximately from 500 to 4000, and particularly preferably from800 to 3000.

(Polycaprolactone Polyols)

The polycaprolactone polyols may be obtained by ring openingpolymerization of ε-caprolactones.

(Polycarbonate Diols)

Exemplary polycarbonate diols include products obtained by condensationbetween divalent alcohols such as 1,4-butanediol and 1,6-hexanediol, andcarbonate compounds such as dimethyl carbonate, diethyl carbonate anddiphenyl carbonate. The polycarbonate diols preferably havenumber-average molecular weights ranging approximately from 500 to 3000,and particularly preferably from 800 to 2000.

<Isocyanate Compound>

The isocyanate compound used in the TPU production may be an aromatic,aliphatic or alicyclic compound having two or more isocyanato groups inthe molecule.

(Aromatic Polyisocyanates)

Exemplary aromatic polyisocyanates include 2,4-tolylene diisocyanate,2,6-tolylene diisocyanate, isomeric mixtures of tolylene diisocyanateswith 2,4-isomer: 2,6-isomer weight ratio of 80:20 (TDI-80/20) or 65:35(TDI-65/35); 4,4′-diphenylmethane diisocyanate, 2,4′-diphenylmethanediisocyanate, 2,2′-diphenylmethane diisocyanate and isomeric mixtures ofarbitrary isomers of these diphenylmethane diisocyanates; toluylenediisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate,p-phenylene diisocyanate and naphthalene diisocyanate.

(Aliphatic Polyisocyanates)

Exemplary aliphatic polyisocyanates include ethylene diisocyanate,trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylenediisocyanate, octamethylene diisocyanate, nonamethylene diisocyanate,2,2′-dimethylpentane diisocyanate, 2,2,4-trimethylhexane diisocyanate,decamethylene diisocyanate, butene diisocyanate,1,3-butadiene-1,4-diisocyanate, 2,4,4-trimethylhexamethylenediisocyanate, 1,6,11-undecamethylene triisocyanate, 1,3,6-hexamethylenetriisocyanate, 1,8-diisocyanato-4-isocyanatomethyloctane,2,5,7-trimethyl-1,8-diisocyanato-5-isocyanatomethyloctane,bis(isocyanatoethyl)carbonate, bis(isocyanatoethyl)ether,1,4-butyleneglycol dipropylether-ω,ω′-diisocyanate, lysinisocyanatomethyl ester, lysin triisocyanate,2-isocyanatoethyl-2,6-diisocyanatohexanoate,2-isocyanatopropyl-2,6-diisocyanatohexanoate andbis(4-isocyanato-n-butylidene)pentaerythritol.

(Alicyclic Polyisocyanates)

Exemplary alicyclic polyisocyanates include isophorone diisocyanate,bis(isocyanatomethyl)cyclohexane, dicyclohexylmethane diisocyanate,cyclohexane diisocyanate, methylcyclohexane diisocyanate,2,2′-dimethyldicyclohexylmethane diisocyanate, dimer acid diisocyanate,2,5-diisocyanatomethyl-bicyclo[2.2.1]-heptane,2,6-diisocyanatomethyl-bicyclo[2.2.1]-heptane,2-isocyanatomethyl-2-(3-isocyanatopropyl)-5-isocyanatomethyl-bicylco[2.2.1]-heptane,2-isocyanatomethyl-2-(3-isocyanatopropyl)-6-isocyanatomethyl-bicyclo[2.2.1]-heptane,2-isocyanatomethyl-3-(3-isocyanatopropyl)-5-(2-isocyanatoethyl)-bicyclo[2.2.1]-heptane,2-isocyanatomethyl-3-(3-isocyanatopropyl)-6-(2-isocyanatoethyl)-bicyclo[2.2.1]-heptane,2-isocyanatomethyl-2-(3-isocyanatopropyl)-5-(2-isocyanatoethyl)-bicyclo[2.2.1]-heptaneand2-isocyanatomethyl-2-(3-isocyanatopropyl)-6-(2-isocyanatoethyl)-bicyclo[2.2.1]-heptane.

These polyisocyanates may be used in modified forms with urethanes,carbodiimides, urethoimines, biurets, allophanates or isocyanurates.

Preferable polyisocyanates include 4,4′-diphenylmethane diisocyanate(MDI), hydrogenated MDI (dicyclohexylmethane diisocyanate (HMDI)),p-phenylene diisocyanate (PPDI), naphthalene diisocyanate (NDI),hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI),2,5-diisocyanatomethyl-bicyclo[2.2.1]-heptane (2,5-NBDI) and2,6-diisocyanatomethyl-bicyclo[2.2.1]-heptane (2,6-NBDI). Of these, MDI,HDI, HMDI, PPDI, 2,5-NBDI and 2,6-NBDI are preferably used. Thesediisocyanates also be preferably used in modified forms with urethanes,carbodiimides, urethoimines or isocyanurates.

<Chain Extender>

The chain extender used in the TPU production is preferably analiphatic, aromatic, heterocyclic or alicyclic, low-molecular weightpolyol having two or more hydroxyl groups in the molecule. The chainextender is preferably dehydrated by being heated under reduced pressureuntil its water content lowers to a sufficient level. The water contentwill be preferably reduced to 0.05 wt % or below, more preferably 0.03wt % or below, and even more preferably 0.02 wt % or below.

The aliphatic polyols include ethylene glycol, propylene glycol,1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol,glycerol and trimethylolpropane. The aromatic, heterocyclic or alicyclicpolyols include p-xylene glycol, bis(2-hydroxyethyl) terephthalate, bis(2-hydroxyethyl) isophthalate, 1,4-bis (2-hydroxyethoxy) benzene,1,3-bis(2-hydroxyethoxy) benzene, resorcin, hydroquinone,2,2′-bis(4-hydroxycyclohexyl) propane,3,9-bis(1,l-dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane,1,4-cyclohexanedimethanol and 1,4-cyclohexanediol.

The chain extenders may be used singly or in combination of two or morekinds.

<Catalyst>

The TPU may be produced under catalysis by a common catalyst, such asorganometallic compounds, widely used in preparing polyurethanes.Suitable catalysts include organometallic compounds such as tin acetate,tin octylate, tin oleate, tin laurate, dibutyltin diacetate, dibutyltindilaurate, dibutyltin dichloride, zinc octanoate, zinc naphthenate,nickel naphthenate and cobalt naphthenate. These catalysts may be usedsingly or in combination or two or more kinds. The catalyst(s) will beused in an amount of 0.0001 to 2.0 parts by weight, and preferably 0.001to 1.0 part by weight, based on 100 parts by weight of the polyol.

<Additives>

The TPU is preferably incorporated with an additive such as a heatstabilizer or a light stabilizer. The additives may be added eitherduring or after the production of the TPU, but preferably they arepreliminary dissolved within the reaction materials during theproduction of the TPU.

The heat stabilizers include hindered phenolic antioxidants, andphosphorous-, lactone- or sulfur-based heat stabilizers. Specificexamples are IRGANOX series 1010, 1035, 1076, 1098, 1135, 1222, 1425WL,1520L, 245, 3790, 5057, IRGAFOS series 168, 126, and HP-136 (allavailable from Ciba Specialty Chemicals).

The light stabilizers include benzotriazole-, triadine- orbenzophenone-based ultraviolet light absorbers, benzoate-based lightstabilizers and hindered amine-based light stabilizers. Specificexamples are TINUVIN P, TINUVIN series 234, 326, 327, 328, 329, 571,144, 765 and B75 (all available from Ciba Specialty Chemicals).

The heat stabilizers and the light stabilizers each are preferably usedin an amount of 0.01 to 1 wt %, andmore preferably 0.1 to 0.8 wt % ofTPU.

The TPU may be optionally incorporated with further additives, includinghydrolysis inhibitors, releasing agents, colorants, lubricants, rustpreventives and fillers.

<Polymer>

The polymer for forming the elastic nonwoven fabric of the presentinvention may consist solely of the aforesaid thermoplastic polyurethaneelastomer (TPU). The polymer may optionally contain other thermoplasticpolymer(s) without adversely affecting the objects of the invention.When the polymer contains TPU and other thermoplastic polymer(s), TPUwill preferably have an amount of 10 wt % or above, more preferably 50wt % or above, still preferably 65 wt % or above, and optimally 75 wt %or above. When the polymer contains 10 wt % or above of the TPU, theelastic nonwoven fabric obtained therefrom will have sufficientelasticity and low residual strain. For example, such elastic nonwovenfabrics may be suitably used in garments, hygiene materials andmaterials for sporting goods that are required to repeatedly exhibitstretching properties.

(Other Thermoplastic Polymers)

The other thermoplastic polymers are not particularly limited if theycan form nonwoven fabrics. Examples thereof include styrene elastomers,polyolefin elastomers, vinyl chloride elastomers, polyesters, esterelastomers, polyamides, amide elastomers, polyolefins such aspolyethylene, polypropylene and polystyrene, and polylactic acids.

The styrene elastomers include diblock and triblock copolymers based ona polystyrene block and either a butadiene rubber block or an isoprenerubber block. These rubber blocks may be unsaturated or completelyhydrogenated. Specific examples of the styrene elastomers includeelastomers commercially available under the trade names of KRATONpolymers (Shell Chemicals), SEPTON (KURARAY CO., LTD.), TUETEC (AsahiKasei Corporation) and LEOSTOMER (RIKEN TECHNOS CO.).

The polyolefin elastomers include ethylene/α-olefin copolymers andpropylene/α-olefin copolymers. Specific examples thereof include TAFMER(Mitsui Chemicals, Inc.), Engage (ethylene/octene copolymer, DuPont DowElastomers) and CATALLOY (crystalline olefin copolymer, MONTELL).

The vinyl chloride elastomers include LEONYL (RIKEN TECHNOS CO., LTD)and Posmere (Shin-Etsu Polymer Co.).

The ester elastomers include HYTREL (E. I. DuPont) and PELPRENE (TOYOBOCO., LTD.).

The amide elastomers include PEBAX (ATOFINA Japan Co., Ltd.).

Other exemplary thermoplastic polymers include DUMILAN (ethylene/vinylacetate/vinyl alcohol copolymer, Mitsui Takeda Chemicals, Inc.), NUCREL(ethylene/(meth)acrylic acid copolymer resin, DUPONT-MITSUIPOLYCHEMICALS CO., LTD.) and ELVALOY (ethylene/acrylic ester/carbonoxide terpolymer, DUPONT-MITSUI POLYCHEMICALS CO., LTD.).

These other thermoplastic polymers may be melt blended with TPU, thenpelletized and thereafter spun. Alternatively, they may be pelletized,then blended with TPU pellets and spun together.

(Additives)

The polymer may contain additives, including various stabilizers such asheat stabilizers and weathering stabilizers, antistatic agents, slipagents, anti-fogging agents, lubricants, dyes, pigments, natural oils,synthetic oils and waxes.

Exemplary stabilizers include anti-aging agents such as2,6-di-t-butyl-4-methylphenol (BHT); phenolic antioxidants such astetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionato]methane,β-(3,5-di-t-butyl-4-hydroxyphenyl) propionic acid alkyl ester,2,2′-oxamidobis[ethyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)]propionate andIrganox 1010 (trade name, hindered phenolic antioxidant) ; metal saltsof fatty acids, such as zinc stearate, calcium stearate and calcium1,2-hydroxystearate; and fatty acid esters of polyvalent alcohols, suchas glycerin monostearate, glycerin distearate, pentaerythritolmonostearate, pentaerythritol distearate and pentaerythritoltristearate. These stabilizers may be used singly or in combination oftwo or more kinds.

<Elastic Nonwoven Fabric>

The elastic nonwoven fabric of the invention is produced by spunbondingthe TPU-containing polymer. The spunbonding may be a conventionaltechnique. For example, the method disclosed in JP-A-60-155765 may beemployed. A specific exemplary process will be given below. First, thepolymer is melt spun through a spinneret into a plurality of fibers.When TPU and other thermoplastic polymer(s) are used in combination,they may be formed into conjugate fibers having a sheath-coreconfiguration, a segmented configuration, an islands-in-the-seaconfiguration or a side-by-side configuration. As used herein, the“conjugate fiber” will refer to a fiber in which there are at least twophases that have a length/diameter ratio which is appropriate for thestrand to be called as a fiber. Here, the diameter will be considered asof the cross section of fiber regarded as a circle. There are threetypes of sheath-core configurations:

a concentric configuration in which the circular core portion and thedoughnut-shaped sheath portion are arranged in concentric relation;

an eccentric configuration in which the core portion is completelyincluded within the sheath portion with their centers apart from oneanother; and

an exposed core configuration in which the core portion is partiallyexposed from the sheath portion due to their centers being far apartfrom one another.

The extruded fibers are subsequently introduced in a cooling chamber,quenched with a cooling air, thereafter drawn by air, and deposited on amoving collecting surface. In the production process:

a die with the spinneret will generally have a temperature of 180 to240° C., preferably 190 to 230° C., and more preferably 200 to 225° C.;the cooling air temperature will generally range from 5 to 50° C.,preferably from 10 to 40° C., and more preferably from 15 to 30° C. fromthe viewpoints of economical efficiency and spinnability; and

the drawing air will generally have a velocity of 100 to 10,000 m/min,and preferably 500 to 10,000 m/min.

The fibers formed as described above generally have diameters of 50 μmor less, preferably 40 μm or less, and more preferably 30 μm or less.The variation in diameter among these fibers is smaller than among meltblown fibers. The fiber diameters are such that the standard deviationthereof (Sn) divided by the average fiber diameter (X_(ave))(Sn/X_(ave)) gives a value of 0.15 or less, preferably 0.12 or less, andmore preferably 0.10 or less. The smaller the Sn/X_(ave) value, theevener the nonwoven fabric surface, leading to remarkable improvement intouch.

Subsequently, after the fiber deposited on a moving collecting surfacein a web form, the deposition is partially entangled or fusion bonded.The entangle treatment may be carried out by needle punching, waterjetting or ultrasonic sealing, and the fusion bonding may be effectedwith a thermal embossing roll. Fusion bonding with a thermal embossingroll is preferably employed. The thermal embossing temperature isusually 50 to 160° C., and preferably 70 to 150° C. The thermalembossing roll may have an arbitrary embossing area percentage, whichalthough is preferably between 5 and 30%.

The heat embossing as described above enables highly improvedproperties, including tensile strength, maximum strength and elongationat break, since the mechanical bonding achieves firmer adhesion amongfibers than does meltblowing where fibers were fusion bondedautomatically by their heat. Also, embossed areas are very resistant tofracture upon elongation so that the residual strain can be reduced.

Such nonwoven fabrics have excellent elasticity and are favorably usedin materials which bring into contact with a skin, such as garments,hygiene materials and materials for sporting goods. The hygienematerials include disposable diapers, sanitary napkins and urineabsorbent pads.

The elastic nonwoven fabric has a tensile strength per basis weight at100% elongation of 1 to 50 gf/basis weight, preferably 1.5 to 30gf/basis weight, and more preferably 2 to 20 gf/basis weight. When thetensile strength is 1 gf/basis weight or above, the elastic nonwovenfabric can exert good body conformability when used in garments, hygienematerials and materials for sporting goods.

The elastic nonwoven fabric ranges in maximum strength per basis weightfrom 5 to 100 gf/basis weight, preferably from 10 to 70 gf/basis weight,and more preferably from 15 to 50 gf/basis weight. Having the maximumstrength of 5 gf/basis weight or above, the elastic nonwoven fabric willbe more resistant to breakage when used in garments, hygiene materialsand materials for sporting goods.

The elastic nonwoven fabric has a maximum elongation of 50 to 1200%,preferably 100 to 1000%, and more preferably 150 to 700%. Whenthemaximumelongation is 50% or more, the elastic nonwoven fabricprovides comfortable fit when used in garments, hygiene materials andmaterials for sporting goods.

The elastic nonwoven fabric has a residual strain of 50% or less,preferably 35% or less, and more preferably 30% or less after 100%elongation. The residual strain of 50% or less can make less noticeablethe deformation of nonwoven fabric products such as garments, hygienematerials and materials for sporting goods.

The elastic nonwoven fabric ranges in basis weight from 3 to 200 g/cm²,and preferably from 5 to 150 g/cm².

Laminate

The elastic nonwoven fabric of the invention may be bonded with anextensible nonwoven fabric to form an elastic laminate having softertouch.

The extensible nonwoven fabric is not particularly limited if it can bestretched to the elastic limit of the elastic nonwoven fabric accordingto the invention. When the laminate is intended for hygiene materialssuch as disposable diapers, the extensible nonwoven fabric is preferablymade up of a polymer containing polyolefin, particularly polyethyleneand/or polypropylene, from the viewpoints of superior touch, highelasticity and excellent heat sealing properties. When the thermalembossing is employed in the production of the laminate, the extensiblenonwoven fabric is preferably comprised of a polymer that has goodcompatibility and bondability with the elastic nonwoven fabric accordingto the invention.

The fibers constituting the extensible nonwoven fabric preferably have amonocomponent configuration, a sheath-core configuration, a segmentedconfiguration, an islands-in-the-sea configuration or a side-by-sideconfiguration. The extensible nonwoven fabric comprises a mixture offibers having the different configurations.

The elastic laminate may be produced by a series of steps in which:

the elastic fibers according to the invention are deposited on acollecting surface by the procedure described hereinabove;

extensible fibers are deposited on the elastic fiber web; and

the elastic fibers and the extensible fibers are entangled or fusionbonded with each other by any method described above to form a laminatecomprising the elastic nonwoven fabric layer and the extensible nonwovenfabric layer. The laminate may also be formed by bonding the elasticnonwoven fabric and the extensible nonwoven fabric by means of anadhesive.

When thermal embossing is employed in the production of the laminate, itis preferably carried out under similar conditions to those describedabove for the elastic nonwoven fabric. Suitable adhesives include resinadhesives such as vinyl acetate adhesives, vinyl chloride adhesives andpolyvinyl alcohol adhesives, and rubber adhesives such asstyrene/butadiene adhesives, styrene/isoprene adhesives and urethaneadhesives. Solution adhesives in organic solvents and aqueous emulsionadhesives of these adhesives may also be used. Of the adhesives,hot-melt rubber adhesives such as styrene/isoprene adhesives andstyrene/butadiene adhesives may be favorably used because of theresultant effect while maintaining soft touch of the laminate.

A laminate of the invention may be produced by laminating athermoplastic polymer film on the layer comprising the elastic nonwovenfabric. The thermoplastic polymer film may be breathable or perforatedfilm.

EXAMPLES

The present invention will be described by the following Examples, butit should be construed that the invention is in no way limited thereto.In Examples and Comparative Examples, TPUs were analyzed and tested todetermine their properties by the procedures illustrated hereinbelow.

(1) Solidifying Point

The solidifying point was obtained on a differential scanningcalorimeter (DSC 220C) connected to a Disc Station Model SSC 5200H(Seiko Instruments Inc.). Approximately 8 mg of the sample, ground TPU,was weighed on an aluminum pan, which was then capped and crimped. Areference was prepared in the same manner using alumina. After thesample and the reference were put in place in the cell, an experimentwas carried out in a nitrogen stream fed at a flow rate of 40 Nml/min.The temperature was raised from room temperature to 230° C. at a rate of10° C./min, maintained at the temperature for 5 minutes, and lowered to−75° C. at a rate of 10° C./min. From the exothermic profile recorded inthis experiment, the starting point (initial rise temperature) of theexothermic peak attributed to the solidification of TPU was obtained asthe solidifying point (C.°).

(2) Number of Polar-Solvent-Insoluble Particles

Polar-solvent-insoluble particles were counted on a particle sizedistribution analyzer Multisizer II (Beckman Coulter, Inc.) based on anelectrical sensing zone method. A 5-L separable flask was charged with3500 g of dimethylacetamide (Wako Special Grade, available from WakoPure Chemical Industries, Ltd.) and 145.83 g of ammonium thiocyanate(special grade, available from JUNSEI CHEMICAL CO., LTD.). They werebrought to a solution at room temperature over a period of 24 hours. Thesolution was filtered through a 1 μm-membrane filter under reducedpressure. A reagent A was thus obtained. Thereafter, 180 g of thereagent A and 2.37 g of TPU pellets were precisely weighed into a 200 ccglass bottle. Soluble components of TPU were allowed to dissolve over aperiod of 3 hours. The solution thus obtained was used as a sample. A100 μm-aperture tube was attached to the Multisizer II, and the existingsolvent in the analyzer was replaced with the reagent A. The pressurewas reduced to nearly 3000 mmAq. Thereafter, the reagent A was weighedin an amount of 120 g into a beaker which had been sufficiently washed.Blank measurement was carried out to provide that pulses appeared at arate of 50 or less per minute. After the optimum current and gain hadbeen set manually, calibration was made using 10 μm standard particlesof uncrosslinked polystyrene. To carry out the measurement, asufficiently washed beaker was charged with 120 g of the reagent A andabout 10 g of the sample. The measurement was conducted for 210 seconds.The number of particles counted during this measurement was divided bythe amount of TPU aspirated into the aperture tube to determine thenumber of polar-solvent-insoluble particles in the TPU (particles/g) Theamount of TPU is calculated by the following formula:TPU amount={(A/100)×B/(B+C)I×Dwherein A is a TPU concentration in the sample (wt %), B is an amount ofthe sample weighted into the beaker, C is an amount of the reagent Aweighted into the beaker, and D is an amount of the solution aspiratedinto the aperture tube during the measurement (for 210 seconds).(3) Ratio of Heat of Fusion Attributed to Hard Domains

The ratio of the heat of fusion attributed to the hard domains wasobtained on a differential scanning calorimeter (DSC 220C) connected toa Disc Station Model SSC 5200H (Seiko Instruments Inc.). Approximately 8mg of the sample, ground TPU, was placed on an aluminum pan, which wasthen capped and crimped. A reference was prepared in the same mannerusing alumina. After the sample and the reference were put in place inthe cell, an experiment was carried out in a nitrogen stream fed at aflow rate of 40 Nml/min. The temperature was raised from roomtemperature to 230° C. at a rate of 10° C./min. From the endothermicprofile recorded in this experiment, the total heat of fusion (a)determined from endothermic peaks within the temperature range of from90 to 140° C. and the total heat of fusion (b) determined fromendothermic peaks within the temperature range of from above 140 to 220°C. were obtained. These values were substituted to the followingequation to determine the ratio of the heat of fusion attributed to thehard domains:Heat of fusion(%)=a/(a+b)×100(4) Melt Viscosity at 200° C.

The melt viscosity (Pa·s) at 200° C. (hereinafter “melt viscosity”) wasdetermined for TPU at a shear rate of 100 sec⁻¹ on a Capirograph Model1C (Toyo Seiki K.K.) having a nozzle 30 mm in length and 1 mm indiameter.

(5) The Water Content in TPU

The water content (ppm) in TPU was measured on a water contentmeasurement device Model AVQ-5S and an evaporator Model EV-6 (bothavailable from HIRANUMA SANGYO Co., Ltd.). Approximately 2 g of TPUpellets were weighed on a pan and introduced into a 250° C. hot oven.The evaporated water was led to a water-free titration cell of the watercontent measurement device and titration was performed using a KarlFischer reagent. When the voltage between the electrodes remainedunchanged for 20 seconds, it was considered that the water content inthe cell had ceased to increase so that the titration was terminated.

(6) Hardness (Shore A)

TPU was tested in accordance with JIS K-7311 at 23° C. and 50% RH todetermine the hardness. A durometer Type A was used in the test.

(7) Average Smallest Fiber Diameter

Melt spinning was performed under the same conditions as in theproduction of a nonwoven fabric except for a drawing rate. In thespinning, the drawing rate for the filaments was stepwise increased by250 m/min until filament breakage took place and lowered therefrom by250 m/min. At the drawing rate determined as described above, the fiberswere drawn under the same conditions as in the production of a nonwovenfabric except for a drawing rate. The drawn fibers were deposited toform a web. This web was defined as a web having smallest fiberdiameters. The image of web having smallest fiber diameters was taken at200-hold magnification, and was analyzed on a dimension measuringsoftware Pixs 2000 Ver 2.0 (Inotech). Diameters were measured forarbitrary 100 fibers and averaged to determine the average smallestfiber diameter (μm) of the fibers.

(8) Average Fiber Diameter and Standard Deviation

The image of a nonwoven fabric in the Examples was taken at 200-holdmagnification by an electron microscope. In Comparative Examples, theimage of broken or fusion bonded fibers in a nonwoven fabric was takenat 200-hold magnification by an electron microscope. The diameters ofarbitral 100 fibers (Xi, unit: μm) in these images were measured. Theresults were averaged to determine the average fiber diameter (X_(ave),unit: μm). The standard deviation (Sn, unit: μm) was obtained from thefollowing equation (n=100).${Sn} = \sqrt{\frac{1}{n - 1}{\sum\limits_{i = 1}^{n}\left( {{Xi} - X_{ave}} \right)^{2}}}$(9) Occurrence of Filament Breakage

Spinning was visually observed from the vicinity of the spinneret tocount the occurrence of filament breakage for 5 minutes (times/5 min).The “filament breakage” was counted when single filament broke duringthe spinning, and was disregarded when adhered filaments broke (whichwas separately counted as fusion bonded fibers)

(10) Occurrence of Fusion Bonded Fibers

Spinning was visually observed from the vicinity of the spinneret tocount the occurrence of fusion bonded fibers for 5 minutes (times/5min).

(11) Maximum Strength and Maximum Elongation

Five specimens, each 5.0 cm in the machine direction (MD) and 2.5 cm inthe cross direction (CD), were cut from a nonwoven fabric. They wereeach stretched at a gap between chucks of 30 mm and a rate of 30 mm/minto determine the elongation at the maximum load. The elongations at themaximum load of the 5 specimens were averaged to determine the maximumelongation (%) The average of the maximum load for the 5 specimens wasdivided by the basis weight to determine the maximum strength (gf/basisweight).

(12) Residual Strain and Tensile Strength

Five specimens, each 5.0 cm in the machine direction (MD) and 2.5 cm inthe cross direction (CD), were cut from a nonwoven fabric. They wereeach stretched to 100% elongation at a gap between chucks of 30 mm and arate of 30 mm/min, thereat measuring the load. Immediately thereafter,each specimen was relaxed to its original length at the same rate andthe strain was measured at a tensile load of 0 gf. The loads at 100%elongation of the 5 specimens were averaged, and the average was dividedby the basis weight to determine the tensile strength (gf/basis weight).The strains of the 5 specimens were averaged to determine the residualstrain (%).

(13) Touch

The above spunbonded nonwoven fabric was evaluated for its touch by 10panelists. The evaluation was made based on the following criteria:

A: 10 out of the 10 panelists said the fabric was nonsticky and nice tothe touch.

B: 9 to 7 out of the 10 panelists said the fabric was nonsticky and niceto the touch.

C: 6 to 3 out of the 10 panelists said the fabric was nonsticky and niceto the touch.

D: 2 or 0 out of the 10 panelists said the fabric was nonsticky and niceto the touch.

TPU Production Example 1

In an atmosphere of nitrogen, 280.3 parts by weight of4,4′-diphenylmethane diisocyanate (hereinafter “MDI”) (trade name:Cosmonate PH, available from Mitsui Takeda Chemicals, Inc.) was placedin an isocyanate compound storage tank (hereinafter “tank A”) and heatedto 45° C. with agitation while avoiding bubbles.

Separately, a polyol storage tank (hereinafter “tank B”) was chargedunder a nitrogen atmosphere with:

219.8 parts by weight of polyester polyol having a number-averagemolecular weight of 1000 (trade name: Takelac U2410, available fromMitsui Takeda Chemicals, Inc.);

439.7 parts by weight of polyester polyol having a number-averagemolecular weight of 2000 (trade name: Takelac U2420, available fromMitsui Takeda Chemicals, Inc.);

2.97 parts by weight of bis(2,6-diisopropyl phenyl) carbodiimide (tradename: Stabilizer 7000, available from RASCHIG GmbH);

2.22 parts by weight of a hindered phenolic antioxidant (trade name:Irganox 1010, available from Ciba Specialty Chemicals); and

2.22 parts by weight of a benzotriazole-based ultraviolet light absorber(trade name: JF-83, available from Johoku Chemical Co., Ltd).

The contents were brought to 90° C. under agitation. This mixture willbe refereed to as the polyol solution 1.

Subsequently, 60.2 parts by weight of a chain extender, 1,4-butanediol(BASF JAPAN), was introduced into a chain extender storage tank(hereinafter “tank C”) in an atmosphere of nitrogen and brought to 50°C.

These materials had amounts that would allow estimation of the hardsegment amount to be 34 wt %.

Thereafter, MDI and the polyol solution 1 were supplied thoughliquid-supply lines with gear pumps and flow meters at constant flowrates of 16.69 kg/h and 39.72 kg/h respectively to a high-speed stirrertemperature-controlled at 120° C. (Model SM40 available from SakuraPlant). After they had been mixed by stirring at 2000 rpm for 2 min, theliquidmixture was supplied to a stirrer-equipped reaction pottemperature-controlled at 120° C. Subsequently, the liquid mixture and1,4-butanediol were supplied from the reaction pot and the tank C atconstant flow rates of 56.41 kg/h and 3.59 kg/h respectively to ahigh-speed stirrer (Model SM40) temperature-controlled at 120° C., andthey were mixed by stirring at 2000 rpm for 2 min. The resultant mixturewas passed though a series of static mixers whose insides had beencoated with Teflon™ or protected with a Teflon™ tube. The static mixerssection consisted of a series of lst to 3rd static mixers whose each is0.5 m in length and 20 mm in inner diameter (temperature: 250° C.) , 4thto 6th static mixers whose each is 0.5 m in length and 20 mm in innerdiameter (temperature: 220° C.) , 7th to 12th static mixers whose eachis 1.0 m in length and 34 mm in inner diameter (temperature: 210° C.),and 13th to 15th static mixers whose each is 0.5 m in length and 38 mmin inner diameter (temperature: 200° C.).

The reaction product discharged from the 15th static mixer wasintroduced via a gear pump into a single-screw extruder (65 mm indiameter, temperature controlled at 200 to 215° C.) which was fitted atan outlet head with a polymer filter (DENA FILTER available from NAGASE& CO. LTD.), and forced through a strand die. The resultant strands werewater-cooled and consecutively cut by a pelletizer. The pellets weremaintained in a dryer at 85 to 90° C. over a period of 8 hours. Thus, athermoplastic polyurethane elastomer (TPU-1) with a water content of 65ppm resulted.

The tests provided that TPU-1 had a solidifying point of 115.6° C. andcontained 1.40×10⁶ polar-solvent-insoluble particles per g. Separately,TPU-1 was injection molded into a specimen, which was found to have ahardness of 86A. TPU-1 had a 200° C. melt viscosity of 2100 Pa·s and aratio of the heat of fusion attributed to the hard domains of 62.8%.

TPU Production Example 2

In a nitrogen atmosphere, 288.66 parts by weight of MDI was introducedinto the tank A and heated to 45° C. with agitation while avoidingbubbles.

Separately, the tank B was charged under a nitrogen atmosphere with:

216.2 parts by weight of polytetramethylene ether glycol having anumber-average molecular weight of 1000 (trade name: PTG-1000, availablefrom Hodogaya Chemicals);

432.5 parts by weight of polyester polyol having a number-averagemolecular weight of 2000 (trade name: Takelac U2720, available fromMitsui Takeda Chemicals, Inc.);

2.22 parts by weight of Irganox 1010; and

2.22 parts by weight of JF-83.

The contents were brought to 95° C. under agitation. This mixture willbe refereed to as the polyol solution 2.

Subsequently, 62.7 parts by weight of a chain extender, 1,4-butanediol,was introduced into the tank C in an atmosphere of nitrogen and broughtto 50° C.

These materials had amounts that would allow estimation of the hardsegment amount to be 35 wt %.

Thereafter, MDI and the polyol solution 2 were supplied thoughliquid-supply lines with gear pumps and flow meters at constant flowrates of 17.24 kg/h and 39.01 kg/h respectively to a high-speed stirrer(Model SM40) temperature-controlled at 120° C. After they had been mixedby stirring at 2000 rpm for 2 min, the liquid mixture was supplied to astirrer-equipped reaction pot temperature -controlled at 120° C.Subsequently, the liquid mixture and 1,4-butanediol were supplied fromthe reaction pot and the tank C at constant flow rates of 56.25 kg/h and3.74 kg/h respectively to a high-speed stirrer (Model SM40)temperature-controlled at 120° C., and they were mixed by stirring at2000 rpm for 2 min. The resultant mixture was passed though a series ofthe static mixers as described in Production Example 1.

The reaction product discharged from the 15th static mixer waspelletized in the same manner as in Production Example 1. The pelletswere maintained in a dryer at 85 to 90° C. over a period of 8 hours.Thus, a thermoplastic polyurethane elastomer (TPU-2) with a watercontent of 70 ppm resulted.

The tests provided that TPU-2 had a solidifying point of 106.8° C. andcontained 150×10⁶ polar-solvent-insoluble particles per g. Separately,TPU-2 was injection molded into a specimen, which was found to have ahardness of 85A. TPU-2 had a 200° C. melt viscosity of 1350 Pa·s and aratio of the heat of fusion attributed to the hard domains of 55.1%.

TPU Production Example 3

A pressure kneader purged with nitrogen was charged with:

100 parts by weight of adipate polyester polyol (trade name: TakelacU2410, available from Mitsui Takeda Chemicals, Inc.);

3.12 parts by weight of 1,4-butanediol;

0.13 part by weight of an amide wax lubricant (stearic acid amide); and

0.38 part by weight of a weathering stabilizer (trade name: SanolLS-770, available from Sankyo Co., Ltd.).

After the contents had been heated to 60° C., 22.46 parts by weight of1,6-hexamethylene diisocyanate (trade name: Takenate 700, available fromMitsui Takeda Chemicals, Inc.) was added with stirring, followed bystirring for 20 minutes. The resultant liquid mixture was poured into astainless steel container and introduced into an oventemperature-controlled at 70° C.; the reaction was carried out in anitrogen atmosphere at 70° C. for 24 hours to obtain TPU in a sheetform. The sheet was gradually cooled to room temperature and crushedinto flakes by a granulator. The flakes were dried under reducedpressure to give a thermoplastic polyurethane elastomer (TPU-3) having awater content of 120 ppm.

The tests provided that TPU-3 had a solidifying point of 55.2° C. andcontained 3.50×10⁶ polar-solvent-insoluble particles per g. Separately,TPU-3 was injection molded into a specimen, which was found to have ahardness of 86 A. TPU-3 had a fluidization initiation temperature of108° C. according to the measurement described in WO99/39037 (Page 9,Lines 3-9).

TPU Production Example 4

In an atmosphere of nitrogen, MDI was placed in the tank A and heated to45° C. with agitation while avoiding bubbles.

Separately, the tank B was charged under a nitrogen atmosphere with:

628.6 parts by weight of polyester polyol having a number-averagemolecular weight of 2000 (trade name: Takelac U2024, available fromMitsui Takeda Chemicals, Inc.);

2.21 parts by weight of Irganox 1010; and

77.5 parts by weight of 1,4-butanediol.

The contents were brought to 95° C. under agitation. This mixture willbe refereed to as the polyol solution 3.

These materials had amounts that would allow estimation of the hardsegment amount to be 37.1 wt %.

Thereafter, MDI and the polyol solution 3 were supplied thoughliquid-supply lines with gear pumps and flow meters at constant flowrates of 17.6 kg/h and 42.4 kg/h respectively to a high-speed stirrer(Model SM40) temperature-controlled at 120° C. After they had been mixedby stirring at 2000 rpm for 2 min, the liquid mixture was passed througha series of static mixers in the same manner as in Production Example 1.The static mixers section consisted of a series of 1st to 3rd staticmixers whose each is 0.5 m in length and 20 mm in inner diameter(temperature: 230° C.), 4th to 6th static mixers whose each is 0.5 minlength and 20 mm in inner diameter (temperature: 220° C.) 7th to 12thstatic mixers whose each is 1.0 m in length and 34 mm in inner diameter(temperature: 210° C.) , and 13th to 15th static mixers whose each is0.5 m in length and 38 mm in inner diameter (temperature: 200° C.).

The reaction product discharged from the 15th static mixer wasintroduced via a gear pump into a single-screw extruder (65 mm indiameter, temperature controlled at 180 to 210° C.) which was fitted atan outlet head with a polymer filter (DENA FILTER available from NAGASE& CO. LTD.) and forced through a strand die. The resultant strands werewater-cooled and consecutively cut by a pelletizer. The pellets weremaintained in a dryer at 100° C. over a period of 8 hours. Thus, athermoplastic polyurethane elastomer with a water content of 40 ppmresulted. The thermoplastic polyurethane elastomer was then continuouslyextruded on a single-screw extruder (50 mm in diameter,temperature-controlled at 180 to 210° C.) and were pelletized. Thepellets were maintained in a dryer at 100° C. over a period of 7 hours.Thus, a thermoplastic polyurethane elastomer (TPU-4) with a watercontent of 57 ppm resulted.

The tests provided that TPU-4 had a solidifying point of 103.7° C. andcontained 1.50×10⁶ polar-solvent-insoluble particles per g. Separately,TPU-4 was injection molded into a specimen, which was found to have ahardness of 86 A. TPU-4 had a 200° C. melt viscosity of 1900 Pa·s and aratio of the heat of fusion attributed to the hard domains of 35.2%.

Example 1

TPU-l prepared in Production Example 1 was melt spun using a spunbondmachine under the conditions of a die temperature of 220° C., an outputof 1.0 g/min per nozzle, a cooling air temperature of 20° C., and adrawing air velocity of 3000 m/min. The spunbond machine used herein wasequipped with a spinneret that had a nozzle diameter of 0.6 mm andnozzle pitches of 8 mm longitudinally and 8 mm transversely. Theresultant fibers of TPU-1 were deposited on a collecting surface to forma web, and the web was embossed at 80° C. with an embossing roll(embossing area percentage: 7%, roll diameter: 15 mm, boss pitches: 2.1mm transversely and longitudinally, boss shape: rhombus). Thus, aspunbonded nonwoven fabric with a basis weight of 100 g/m² was obtained.The spunbonded nonwoven fabric was evaluated by the aforementionedmethods. The results are set forth in Table 1.

Example 2

A spunbonded nonwoven fabric was prepared and evaluated by the procedureillustrated in Example 1 except that TPU-1 was replaced by TPU-2. Theresults are set forth in Table 1.

Example 3

An ethylene/vinyl acetate/vinyl alcohol copolymer (trade name: DumilanC1550, available from Mitsui Takeda Chemicals, Inc.) was dehydrated to awater content of 78 ppm by a drier at 70° C. over a period of 8 hours.

TPU-2 and the ethylene/vinyl acetate/vinyl alcohol copolymer were meltblended in amounts of 95 parts by weight and 5 parts by weightrespectively and thereafter pelletized. The solidifying point of theobtained polymer blend was 104.2° C. Separately, the polymer blend wasinjection molded into a specimen, which was found to have a hardness of85 A.

A spunbonded nonwoven fabric was prepared and evaluated by the procedureillustrated in Example 1 except that TPU-1 was replaced by the polymerblend. The results are set forth in Table 1.

Example 4

A styrene/ethylene/propylene/styrene block copolymer (SEPS) (trade name:SEPTON 2002, available from KURARAY CO., LTD.) was dehydrated to a watercontent of 58 ppm by a drier at 80° C. over a period of 8 hours.Separately, an ethylene/α-olefin copolymer (trade name: TAFMER A-35050,available from Mitsui Chemicals, Inc.) was dehydrated to a water contentof 50 ppm by a drier at 75° C. over a period of 8 hours.

TPU-2, SEPTON 2002 and the ethylene/α-olefin copolymer were melt blendedin amounts of 80 parts by weight, 15 parts by weight and 5 parts byweight respectively and thereafter pelletized. The solidifying point ofthe obtained polymer blend was 98.2° C. Separately, the polymer blendwas injection molded into a specimen, which was found to have a hardnessof 85 A.

A spunbonded nonwoven fabric was prepared and evaluated by the procedureillustrated in Example 1 except that TPU-1 was replaced by the polymerblend. The results are set forth in Table 1.

Example 5

A styrene/ethylene/propylene/styrene block copolymer (SEPS) (trade name:SEPTON 2004, available from KURARAY CO., LTD.) was dehydrated to a watercontent of 62 ppm by a drier at 80° C. over a period of 8 hours.

TPU-2 and SEPTON 2004 were melt blended in amounts of 45 parts by weightand 55 parts by weight respectively and thereafter pelletized. Thesolidifying point of the obtained polymer blend was 90.7° C. Separately,the polymer blend was injection molded into a specimen, which was foundto have a hardness of 82 A.

A spunbonded nonwoven fabric was prepared and evaluated by the procedureillustrated in Example 1 except that TPU-1 was replaced by the polymerblend. The results are set forth in Table 1.

Example 6

A spunbonded nonwoven fabric was prepared and evaluated by the procedureillustrated in Example 1 except that TPU-1 was replaced by TPU-4. Theresults are set forth in Table 1.

Example 7

A spunbonded nonwoven fabric was prepared and evaluated by the procedureillustrated in Example 6 except that the basis weight was changed from100 g/m² to 40 g/m². The results are set forth in Table 1.

Example 8

A spunbonded nonwoven fabric was prepared and evaluated by the procedureillustrate in Example 1 except that TPU-4 and a propylene homopolymer(hereinafter “PP-1”) that had MFR (ASTM D1238, 230° C., 2.16 kg load) of60 g/10 min, a density of 0.91 g/cm³ and a melting point of 160° C.,were melt spun in 50/50 weight ratio by a spunbond machine equipped witha hollow, eight-segmented spinneret. The results are set forth inTable 1. TABLE 1 Ex. 1 Ex. 2 Ex. 3 Polymer (wt %) TPU-1 (100) TPU-2(100) TPU-2 (95) C1550 (5) Fiber configuration Monocomponent fiberMonocomponent fiber Monocomponent fiber Solidifying point of TPU 115.6°C. 106.8° C. 106.8° C. Polar-solvent-insoluble particles in TPU 1.40 ×10⁶/g 1.50 × 10⁶/g 1.50 × 10⁶/g Shore A hardness of TPU 86 85 85 Fiberforming method Spunbonding Spunbonding Spunbonding Fiber bonding methodThermal embossing Thermal embossing Thermal embossing Basis weight 100g/m² 100 g/m² 100 g/m² Average smallest fiber diameter (μm) 25.5 27.628.3 Standard deviation Sn (μm) 2.5 2.4 2.6 Sn/X_(ave) 0.10 0.09 0.09Occurrence of filament breakage 0 0 0 (times/5 min) Occurrence of fusionbonded fibers 0 0 0 (times/5 min) Maximum strength (gf/basis weight) 2122 20 Residual strain (%) 20 20 21 Tensile strength (gf/basis weight)5.0 5.0 4.3 Maximum elongation (%) 540 550 480 Touch B B B Ex. 4 Ex. 5Ex. 6 Polymer (wt %) TPU-2 (80) TPU-2 (45) TPU-4 (100) SEPS 2002 (15)SEPS 2004 (55) A-35050 (5) Fiber configuration Monocomponent fiberMonocomponent fiber Monocomponent fiber Solidifying point of TPU 106.8°C. 106.8° C. 103.7° C. Polar-solvent-insoluble particles in TPU 1.50 ×10⁶/g 1.50 × 10⁶/g 1.50 × 10⁶/g Shore A hardness of TPU 85 85 86 Fiberforming method Spunbonding Spunbonding Spunbonding Fiber bonding methodThermal embossing Thermal embossing Thermal embossing Basis weight 100g/m² 100 g/m² 100 g/m² Average smallest fiber diameter (μm) 29.3 28.326.0 Standard deviation Sn (μm) 2.6 2.6 2.5 Sn/X_(ave) 0.09 0.09 0.10Occurrence of filament breakage 0 0 0 (times/5 min) Occurrence of fusionbonded fibers 0 0 0 (times/5 min) Maximum strength (gf/basis weight) 2015 22 Residual strain (%) 21 27 15 Tensile strength (gf/basis weight)4.1 3.8 6.0 Maximum elongation (%) 400 450 670 Touch B B B Ex. 7 Ex. 8Polymer (wt %) TPU-4 (100) TPU-4 (50) PP-1 (50) Fiber configurationMonocomponent fiber Eight-segmented conjugate fiber Solidifying point ofTPU 103.7° C. 103.7° C. Polar-solvent-insoluble particles in TPU 1.50 ×10⁶/g 1.50 × 10⁶/g Shore A hardness of TPU 86 86 Fiber forming methodSpunbonding Spunbonding Fiber bonding method Thermal embossing Thermalembossing Basis weight 40 g/m² 100 g/m² Average smallest fiber diameter(μm) 26.0 30.0 Standard deviation Sn (μm) 2.5 3.0 Sn/X_(ave) 0.10 0.10Occurrence of filament breakage 0 0 (times/5 min) Occurrence of fusionbonded fibers 0 0 (times/5 min) Maximum strength (gf/basis weight) 20 28Residual strain (%) 15 50 Tensile strength (gf/basis weight) 4.0 20Maximum elongation (%) 400 260 Touch B A

Comparative Example 1

A thermoplastic polyurethane elastomer (trade name: ElastollanXET-275-10MS, available from BASF Japan Ltd.) had a solidifying point of60.2° C. and a hardness of 75 A, and contained 1.40×10⁶polar-solvent-insoluble particles per g. This polyurethane elastomer wasdehydrated to a water content of 89 ppm by a drier at 100° C. over aperiod of 8 hours.

A spunbonded nonwoven fabric was prepared and evaluated by the procedureillustrated in Example 1 except that TPU-1 was replaced by ElastollanXET-275-10MS. In this case, the production suffered bad spinnabilitywith many fibers adhering to the spinning tower wall. Further, a part ofthe spunbonded nonwoven fabric adhered to a thermal embossing roll inthe embossing. The results are set forth in Table 2.

Comparative Example 2

A thermoplastic polyurethane elastomer (trade name: Elastollan 1180A-10,available from BASF Japan Ltd.) had a solidifying point of 78.4° C. anda hardness of 82 A, and contained 3.20×10⁶ polar-solvent-insolubleparticles per g. This polyurethane elastomer was dehydrated to a watercontent of 115 ppm by a drier at 100° C. over a period of 8 hours.

Elastollan 1180A-10 was spunbonded under the same conditions as forTPU-1 in Example 1, but many fibers broke in the spinning tower whenthey had been attenuated to diameters of 50 μm or below. The resultantproduct was unusable as a nonwoven fabric. Therefore, the spunbondingwas carried out again while making fibers thick to diameters in which anonwoven fabric could be obtained. However, this spunbonding alsoproduced a nonwoven fabric containing broken fibers, deteriorating thetouch. The nonwoven fabric was evaluated by the methods describedhereinabove. The results are set forth in Table 2.

Comparative Example 3

A thermoplastic polyurethane elastomer (trade name: Elastollan ET-385,available from BASF Japan Ltd.) had a solidifying point of 86.9° C. anda hardness of 84 A, and contained 2.80×10⁶ polar-solvent-insolubleparticles per g. This polyurethane elastomer was dehydrated to a watercontent of 89 ppm by a drier at 100° C. over a period of 8 hours.

Elastollan ET-385 was melt blown under the conditions of a dietemperature of 230° C. and-an output of 2.0 g/min per nozzle, instead ofTPU-1. The fibers were deposited on a collecting surface andautomatically fusion bonded together by their heat. Thus, a melt blownnonwoven fabric with a basis weight of 100 g/m² was obtained.

The nonwoven fabric comprised fine fibers, but the diameters variedbroadly among the fibers and the touch was inferior. The results of theevaluations for the nonwoven fabric are set forth in Table 2.

Comparative Example 4

TPU-3 was spunbonded under the same conditions for TPU-1 in Example 1,but many fibers broke in the spinning tower when they had beenattenuated to diameters of 50 μm or below. Further, some fibers adheredto a thermal embossing roll in the embossing. The resultant product wasso unsatisfactory that some evaluations were avoided. The results areset forth in Table 2. TABLE 2 Comp. Ex. 1 Comp. Ex. 2 Polymer (wt %)XET-275-10MS (100) 1180A-10 (100) Fiber configuration Monocomponentfiber Monocomponent fiber Solidifying point of TPU 60.2° C. 78.4° C.Polar-solvent-insoluble particles in TPU 1.40 × 10⁶/g 3.20 × 10⁶/g ShoreA hardness of TPU 75 82 Fiber forming method Spunbonding SpunbondingFiber bonding method Thermal embossing Thermal embossing Basis weight100 g/m² 100 g/m² Average smallest fiber diameter (μm) 40.1 53.0Standard deviation Sn (μm) 2.5 3.9 Sn/X_(ave) 0.175 0.230 Occurrence offilament breakage (times/5 min) 0 10 Occurrence of welded filaments(times/5 min) 4 0 Maximum strength (gf/basis weight) 19 21 Residualstrain (%) 18 19 Tensile strength (gf/basis weight) 2.0 2.6 Maximumelongation (%) 500 490 Touch D D Comp. Ex. 3 Comp. Ex. 4 Polymer (wt %)ET-385 (100) TPU-3 (100) Fiber configuration Monocomponent fiberMonocomponent fiber Solidifying point of TPU 86.9° C. 55.2° C.Polar-solvent-insoluble particles in TPU 2.80 × 10⁶/g 3.50 × 10⁶/g ShoreA hardness of TPU 84 86 Fiber forming method Meltblowing SpunbondingFiber bonding method Automatic fusion bonding Thermal embossing Basisweight 100 g/m² 100 g/m² Average smallest fiber diameter (μm) 26.4 55.0Standard deviation Sn (μm) 4.3 4.3 Sn/X_(ave) 0.163 0.258 Occurrence offilament breakage (times/5 min) 0 14 Occurrence of welded filaments(times/5 min) — 8 Maximum strength (gf/basis weight) 15 — Residualstrain (%) 30 — Tensile strength (gf/basis weight) 3.7 — Maximumelongation (%) 490 — Touch C D

Example 9

A propylene homopolymer (hereinafter “PP-2”) that had MFR (ASTM D1238,230° C., 2.16 kg load) of 15 g/10 min, a density of 0.91 g/cm³ and amelting point of 160° C., and PP-1 were melt spun by spunbondingtechnique to form concentric sheath-core conjugate fibers in which thecores consisted of PP-2 and the sheaths consisted of PP-1 with a weightratio of 10/90 (cores/sheaths) The concentric conjugate fibers weredeposited on a collecting surface to form a web (hereinafter “web-1”)with a basis weight of 20 g/m².

Subsequently, TPU-4 was melt spun under the same conditions as inExample 6 and deposited on the web-1 to form another web (hereinafter“web-2”) with a basis weight of 40 g/m². Thereafter, PP-1 and PP-2 weremelt spun into concentric sheath-core conjugate fibers as describedabove and deposited on the web-2 to form an additional web (hereinafter“web-3”) with a basis weight of 20 g/m².

The three-layer deposit was embossed at 100° C. with an embossing roll(embossing area percentage: 7%, roll diameter: 150 mm, boss pitches: 2.1mm transversely and longitudinally, boss shape: rhombus). Thus, alaminate of extensible nonwoven fabric/elastic nonwovenfabric/extensible nonwoven fabric, with a basis weight of 80 g/m², wasobtained.

The spunbonded nonwoven fabric laminate was evaluated by theaforementioned methods. For the laminate, the tensile test was carriedout twice under the identical conditions: first to measure a tensilestrength at 100% elongation and second to measure a tensile strength at100% elongation after relaxed to its original length in the first test.The results are set forth in Table 3. TABLE 3 Ex. 9 Fiber forming methodSpunbonding First Fiber configuration Concentric sheath-core layerconjugate fiber Core Sheath Polymer (wt %) PP-2 (100) PP-1 (100) Weightratio (%) 10 90 Basis weight 20 g/m² Second Fiber configurationMonocomponent fiber layer Polymer (wt %) TPU-4 (100) Solidifying pointof TPU 103.7° C. Polar-solvent-insoluble particles 1.50 × 10⁶/g in TPUShore A hardness of TPU 86 Basis weight 40 g/m² Average smallest fiberdiameter (μm) 26.0 Standard deviation Sn (μm) 2.5 Sn/X_(ave) 0.10Occurrence of filament breakage 0 (times/5 min) Occurrence of weldedfilaments 0 (times/5 min) Third Fiber configuration Concentricsheath-core layer conjugate fiber Core Sheath Polymer (wt %) PP-2 (100)PP-1 (100) Weight ratio (%) 10 90 Basis weight 20 g/m² Bonding methodThermal embossing Maximum strength (gf/basis weight) 16 Residual strain(%) 20 Tensile strength (1st measurement) 12.0 (gf/basis weight) Tensilestrength (2nd measurement) 10.0 (gf/basis weight) Maximum elongation (%)200 Touch A

INDUSTRIAL APPLICABILITY

The elastic nonwoven fabric according to the invention has highelasticity, small residual strain, excellent flexibility, narrow fiberdiameter distribution and pleasant touch. Therefore, it can be suitablyused in hygiene materials, industrial materials, garments and materialsfor sporting goods.

1. A spunbonded elastic nonwoven fabric comprising fibers formed from apolymer comprising a thermoplastic polyurethane elastomer, saidthermoplastic polyurethane elastomer having a solidifying point of 65° Cor above as measured by a differential scanning calorimeter (DSC) andcontaining 3.00×10⁶ or less polar-solvent-insoluble particles per g ascounted on a particle size distribution analyzer, which is based on anelectrical sensing zone method, equipped with an aperture tube having anorifice of 100 μm in diameter, and said fibers having diameters suchthat the standard deviation of fiber diameters (Sn) divided by theaverage fiber diameter (X_(ave)) (Sn/X_(ave)) gives a value of 0.15 orless.
 2. The elastic nonwoven fabric according to claim 1, wherein thepolymer contains the thermoplastic polyurethane elastomer in an amountof 10 wt % or more.
 3. The elastic nonwoven fabric according to claim 1,wherein on the thermoplastic polyurethane elastomer, a total heat offusion (a) determined from endothermic peaks within the temperaturerange of from 90 to 140° C. and a total heat of fusion (b) determinedfrom endothermic peaks within the temperature range of from above 140 to220° C., which are measured by a differential scanning calorimeter(DSC), satisfy the following relation (1):a/(a+b)×100≦80   (1).
 4. A hygiene material comprising the elasticnonwoven fabric described in claim
 1. 5. A production method for anelastic nonwoven fabric comprising fibers formed from a polymercomprising a thermoplastic polyurethane elastomer by spunbonding thepolymer, wherein the thermoplastic polyurethane elastomer has asolidifying point of 65° C. or above as measured by a differentialscanning calorimeter (DSC) and contains 3.00×10⁶ or lesspolar-solvent-insoluble particles per g as counted on a particle sizedistribution analyzer, which is based on an electrical sensing zonemethod, equipped with an aperture tube having an orifice of 100 μm indiameter, and wherein the fibers have diameters such that the standarddeviation of fiber diameters (Sn) divided by the average fiber diameter(X_(ave)) (Sn/X_(ave)) gives a value of 0.15 or less.
 6. A spunbondingprocessible thermoplastic polyurethane elastomer that has a solidifyingpoint of 65° C. or above as measured by a differential scanningcalorimeter (DSC), contains 3.00×10⁶ or less polar-solvent-insolubleparticles per g as counted on a particle size distribution analyzer,which is based on an electrical sensing zone method, equipped with anaperture tube having an orifice of 100 μm in diameter, and enablesproduction of spunbonded elastic nonwoven fabrics in which the standarddeviation of fiber diameters (Sn) divided by the average fiber diameter(X_(ave)) (Sn/X_(ave)) gives a value of 0.15 or less.
 7. The elasticnonwoven fabric according to claim 2, wherein on the thermoplasticpolyurethane elastomer, a total heat of fusion (a) determined fromendothermic peaks within the temperature range of from 90 to 140° C. anda total heat of fusion (b) determined from endothermic peaks within thetemperature range of from above 140 to 220° C., which are measured by adifferential scanning calorimeter (DSC), satisfy the following relation(1):a/(a+b)×100≦80   (1).
 8. A hygiene material comprising the elasticnonwoven fabric described in claim
 2. 9. A hygiene material comprisingthe elastic nonwoven fabric described in claim
 3. 10. A hygiene materialcomprising the elastic nonwoven fabric described in claim 7.